The use of hydrogen peroxide (H2O2) in surgery for its antiseptic properties has been associated with life-threatening complications. We report a case of severe oxygen embolism after wound irrigation with H2O2 in a 17-year-old boy undergoing surgical dressing of a large thigh trauma under general anaesthesia. During muscle lavage with 400 mL of H2O2 3%, severe shock suddenly occurred. On the basis of clinical presentation, the diagnosis of pulmonary gas embolism was strongly suspected. Symptomatic treatment initiated immediately, restaured a normal haemodynamic state within a few minutes and the patient recovered without sequelae. The degradation of H2O2 results in considerable amounts of gaseous oxygen. One mL of H2O2 can produce in the tissues 10 mL of oxygen. This gas can enter the circulation and determine severe embolism. The treatment should be initiated without delay. The administration of H2O2 under pressure is contraindicated during surgery.